I have an original Core Duo Macbook 1.83ghz. Doing what you've described doesn't make it spin up at all. That sounds very light duty. There must be something else going on using up CPU. If so, it will likely do it on the MBA as well.
Could be some flash websites, or whatever you're using to play the mp2s or maybe something else unrelated. Bring up Activity Monitor and sort by CPU and see whats using it up. The MBA is very sensitive to video encoding. If its something supported by the very powerful GPU, then it plays it without breaking a sweat. But if its high def and needs the CPU to decode, thats the prime candidate for spinning up the fan.
thanks for everyones thoughts.
yes, what i am running to decode HD video (mp2 format) is Eyetv which is fairly processor intensive for the old macbook with integrated graphics...eats up about 75-80% of the CPU capacity and hence it warms up...
i don't think it has anything to do with flash.
i realized yesterday one thing that i wasn't expecting: the new macbook airs don't have the IR port for the remote...
that's a bummer for my application since i have my universal remote now that can control both my 2 channel stereo and home theater and my macbook so i can do whatever i want from the couch using one remote. since the macbook air doesn't haven't the IR port, i'm having to reconsider my options. :\
the macbook still works for this "DVR playback" capability but who knows for how long.
sigh...
i don't think the latest macbook has an IR port either so i'm now sort of stuck...
may still buy a MBA, but this definitely is a new wrinkle i wasn't expecting...